Override search function

function accommodation_search_forms($form) {
    $form = '
    <div class="search-widget search-form">
        <form method="get" class="searchform" action="' . esc_url(home_url('/')) . '" id="search">
            <div class="input-group">
                <span class="input-group-addon"><span class="glyphicon glyphicon-search"></span></span>
                <input type="text" name="s" class="form-control"  placeholder="' . esc_attr__('Search...', 'accommodation') . '" value="' . get_search_query() . '">
            </div>
        </form>
    </div>';
    return $form;
}

add_filter('get_search_form', 'accommodation_search_forms', 100);